An effective scatter correction method based on single scatter simulation for a 3D whole-body PET scanner

Hamamatsu SHR74000 is a newly designed full three-dimensional （3D） whole body positron emission tomography （PET） scanner with small crystal size and large field of view （FOV）.With the improvement of sensitivity,the scatter events increase significantly at the same time,especially for large objects.Monte Carlo simulations help us to understand the scatter phenomena and provide good references for scatter correction. In this paper,we introduce an effective scatter correction method based on single scatter simulation for the new PET scanner,which accounts for the full 3D scatter correction.With the results from Monte Carlo simulations,we implement a new scale method with special concentration on scatter events from outside the axial FOV and multiple scatter events.The effects of scatter correction are investigated and evaluated by phantom experiments;the results show good improvements in quantitative accuracy and contrast of the images,even for large objects.

Sparsity-based efficient simulation of cluster targets electromagnetic scattering

An efficient and real-time simulation method is proposed for the dynamic electromagnetic characteristics of cluster targets to meet the requirements of engineering practical applications.First,the coordinate transformation method is used to establish a geometric model of the observation scene,which is described by the azimuth angles and elevation angles of the radar in the target reference frame and the attitude angles of the target in the radar reference frame.Then,an approach for dynamic electromagnetic scattering simulation is proposed.Finally,a fast-computing method based on sparsity in the time domain,space domain,and frequency domain is proposed.The method analyzes the sparsity-based dynamic scattering characteristic of the typical cluster targets.The error between the sparsity-based method and the benchmark is small,proving the effectiveness of the proposed method.

Three-dimensional Monte Carlo simulation of bulk fin field effect transistor

In this paper, we investigate the performance of the bulk fin field effect transistor （FinFET） through a three- dimensional （3D） full band Monte Carlo simulator with quantum correction. Several scattering mechanisms, such as the acoustic and optical phonon scattering, the ionized impurity scattering, the impact ionization scattering and the surface roughness scattering are considered in our simulator. The effects of the substrate bias and the surface roughness scattering near the Si/SiO2 interface on the performance of bulk FinFET are mainly discussed in our work. Our results show that the on-current of bulk FinFET is sensitive to the surface roughness and that we can reduce the substrate leakage current by modulating the substrate bias voltage.

In situ grazing-incidence small-angle X-ray scattering observation of block-copolymer templated formation of magnetic nanodot arrays and their magnetic properties

The fabrication of bit-patterned media （BPM） is crucial for new types of hard disk drives. The development of methods for the production of BPM is progressing rapidly. Conventional lithography reaches the limit regarding lateral resolution, and new routes are needed. In this study, we mainly focus on the dependence of the size and shape of magnetic nanodots on the Ar＋-ion etching duration, using silica dots as masks. Two-dimensional （2D） arrays of magnetic nanostructures are created using silica-filled diblock-copolymer micelles as templates. After the self-assembly of the micelles into 2D hexagonal arrays, the polymer shell is removed, and the SiO2 cores are utilized to transform the morphology into a （Co/Pt）2-multilayer via ion etching under normal incidence. The number of preparation steps is kept as low as possible to simplify the formation of the nanostructure arrays. High-resolution in situ grazing-incidence small-angle X-ray scattering （GISAXS） investigations are performed during the Ar＋-ion etching to monitor and control the fabrication process. The in situ investigation provides information on how the etching conditions can be improved for further ex situ experiments. The GISAXS patterns are compared with simulations. We observe that the dots change in shape from cylindrical to conical during the etching process. The magnetic behavior is studied by utilizing the magneto-optic Kerr effect. The Co/Pt dots exhibit different magnetic behaviors depending on their size, interparticle distance, and etching time. They show ferromagnetism with an easy axis of magnetization perpendicular to the film. A systematic dependence of the coercivitv on the dot size is observed.